Optical pickup apparatus for reading and recording information on recording media

Abstract

An optical pickup apparatus for reading and recording information on recording media includes a semiconductor laser, a collimating lens, a half mirror, a reflecting mirror, and an objective lens. Further included therein are a super-resolution cutoff filter and an aperture control filter, one of which is appropriately selected and set right before the objective lens by a filter switching-over device. When reading the DVD, the super-resolution cutoff filter is set at the optical path, whereas when reading the CD, the aperture control filter is set thereat. The filter switching device is arranged separately from an actuator driving system having the objective lens integrally structured therewith.

1. An optical pickup apparatus for reading and recording information on recording media, the apparatus comprising:
 a semiconductor laser for emitting a laser beam; 
 a collimating lens for collimating the laser beam emitted from the semiconductor laser; 
 a super-resolution cutoff filter composed of a polarizing filter layer; 
 an aperture control filter; 
 an objective lens for converging the laser beam onto one recording medium of two kinds each having a different recording density from other; 
 a λ/4 phase plate provided between the super-resolution cutoff filter and the objective lens; 
 a photo-detector for detecting a reflected laser beam from the one recording medium of two kinds; and 
 a filter switching-over means adapted to appropriately select one of the super-resolution cutoff filter combined with the λ/4 phase plate, and the aperture control filter according to the one recording medium in use and to switch over. 
 
     
     
       2. An optical pickup apparatus according to  claim 1 , wherein when information on a recording medium having a high recording density is read and recorded, the super-resolution cutoff filter combined with the λ/4 phase plate is selected, and when information on a recording medium having a low recording density is read and recorded, the aperture control filter is selected.